For grounding less is more
as using to many cables introduce a loop as cables lengths and resistances different this will cause a small difference in voltages that can be amplified
so one cable to one common point is the solution.

For the turn Table this is normally double insulated same as to say it does not have a ground on the mains plug
so the screen wire for the arm is connected to the grounding lug on the chassis
This make a really convenient place where to connect the ground cables from the phono boards

Same cartridges use the left cold wire as ground as well but this is as far as I know for MM cart so no problems
And is your TT got a ground cable on the mains plug you don't need the connection to the ground lug (main rule for avoiding ground loops is use only one cable to each point)

So use insulated plugs or if those are not get your snips and cut the screen cable as the metal enclosure will became your wire.

Here is Sketch of bus of stars
this is if you use 2 box set up
the input and output cables sockets must be isolated from the enclosure as those are grounded on the PCB

This means that 4 wires came from cartridge and all 4 are isolated from the ground

Mains ground to star/chassis-ground connection needs to be decoupled (DDCR) otherwise the mains-ground in the player connected to the player chassis will form a ground-loop via the common-wire that connects RIAA-signal-ground with player-signal-ground. If needed (preferred it is) a separate signal-ground and chassis-ground should also be created in the player, and then you will have the proposed 6-wire RIAA to player connection.

Mains ground to star/chassis-ground connection needs to be decoupled (DDCR) otherwise the mains-ground in the player connected to the player chassis will form a ground-loop via the common-wire that connects RIAA-signal-ground with player-signal-ground. If needed (preferred it is) a separate signal-ground and chassis-ground should also be created in the player, and then you will have the proposed 6-wire RIAA to player connection.

Correct if you have a player with a chassis
Mine and most budgets are double insulated (mains plug has only live and neutral conductors) as mentioned and body is made of MDF
So I only need to ground the arm

Correct if you have a player with a chassis
Mine and most budgets are double insulated (mains plug has only live and neutral conductors) as mentioned and body is made of MDF
So I only need to ground the arm